[BUGFIX] Post-rejoin dial splitting

Ensure that splitting a dial rejoined to an alternative target (eg a mixer) or merged with another dial can still be split properly.

Fixes #372
[BUGFIX] Revert potentially breaking change to logging
[BUGFIX] Avoid logging that is hanging the app
[BUGFIX] Ensure that hungup calls and merged dials can split/rejoin properly
[BUGFIX] Only try to split joined peers and log which peers are going to be unjoined
[BUGFIX] Dial calls should be a unique set
Merge pull request #375 from adhearsion/feature/dial_fixes

Dial fixes